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Posted to common-dev@hadoop.apache.org by "Daryn Sharp (JIRA)" <ji...@apache.org> on 2013/09/12 01:35:52 UTC

[jira] [Created] (HADOOP-9956) RPC listener inefficiently assigns connections to readers

Daryn Sharp created HADOOP-9956:
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             Summary: RPC listener inefficiently assigns connections to readers
                 Key: HADOOP-9956
                 URL: https://issues.apache.org/jira/browse/HADOOP-9956
             Project: Hadoop Common
          Issue Type: Sub-task
          Components: ipc
    Affects Versions: 2.0.0-alpha, 3.0.0
            Reporter: Daryn Sharp
            Assignee: Daryn Sharp


The socket listener and readers use a complex synchronization to update the reader's NIO {{Selector}}.  Updating active selectors is not thread-safe so precautions are required.

However, the current locking choreography results in a serialized distribution of new connections to the parallel socket readers.  A slower/busier reader can stall the listener and throttle performance.

The problem manifests as unexpectedly low cpu utilization by the listener and readers (~20-30%) under heavy load.  The call queue is shallow when it should be overflowing.

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